Ophthalmic surgeons and supporting personnel widely employ particular known systems for irrigation of the eye and the extraction of matter during eye surgery. In one widely used system, the eye is constantly irrigated with a sterile solution during the operation, and the irrigating fluid, as well as particle matter, fragments and the like are drawn off along an aspiration line via a suction tip. This system is particularly used in both phacoemulsification and extra capsular cataract extraction (ECCE) procedures for the exraction of the lens of an eye in which a cataract has developed.
A flow control device which vents to atmosphere is also employed in communication with this aspiration line. The control device is operated by the surgeon, so that aspiration can be modulated in accordance with his immediate needs during surgery. Need may also arise to terminate aspiration suddenly upon engagement of the suction tip against cortical or lens material, or line clogging.
In these systems, the lines and vent controls are typically presterilized and used only once to avoid the danger of cross-contamination between successive patients. It will be appreciated that if fluid from one patient penetrates a permanent part of the structure, the danger of entry of bacteria back into the flow control device with a new patient remains. Although such devices are usually treated as disposables, this is not a necessary condition.
In an early phase of usage of these systems, a T connector was installed in the flexible lines between the suction tip and the aspiration device. A straight through line provided fluid flow, while the branch arm of the T led through a one-way check valve to a vent device controlled by the foot pedal. This configuration was less than satisfactory, because the T connector was subject to sideways movement that could pinch the lines.
As described in U.S. Pat. No. 4,418,944 in identifying certain prior art, a different "fluid coupling" was known in which a male member having a resilient face could be inserted into a cylindrical receptacle of a female member and subjected to a camming action when rotating into a coupling position. In this position, conduits in the female member and the face of the male member became aligned, so that flow could be established. The patent alleged that no straight-through flow was used with this prior device.
U.S. Pat. No. 4,418,944 therefore proposed that this camming action could be utilized to provide venting in an aspiration-irrigation system, by adding a straight-through fluid connection through the male member. Venting conduits in the face of the male member and in the female receptacle were to be aligned when the male member was engaged in position, and in communication with the straight-through fluid line to provide the desired venting action. This type of male member is now widely used, but has been found to be subject to bacterial intrusion. This occurs both because the irrigation fluid can wet the vent line in the permanent female receptacle and because venting introduces non-sterile air. Although not shown in U.S. Pat. No. 4,418,944, this fluid coupling system also incorporates a pair of check valves in the female receptacle. These valves are subject to accumulation of fluids and salts and further introduce danger of possible clogging and cross-contamination.
Because the aspiration-irrigation equipment is expensive and the male member and flexible tubing are relatively low cost so as to be disposable, and because there is a large inventory in use of the equipmemt itself, it is desirable to be able to employ the existing systems, including the female receptacle. However it is also desirable to provide a male member that will fit into the female receptacle and provide controlled venting action but not be subject to the danger of cross-contamination from air or liquid.